Field of the Invention
The present invention relates to an object information acquiring apparatus and an image processing method.
Description of the Related Art
An ultrasound diagnostic apparatus radiates an ultrasound wave from an ultrasound probe into an object, receives the ultrasound wave reflected on a tissue of the object, and forms a tissue image of an organism. Since the ultrasound diagnostic apparatus is noninvasive to the organism, the ultrasound diagnostic apparatus is used in many medical fields. In an ultrasound image obtained by the ultrasound diagnostic apparatus, granular pattern noise called speckle noise sometimes occurs. The speckle noise is noise caused by interference of waves scattered by innumerable small reflectors in the object. The noise could be a hindrance to diagnosis. Therefore, it is desirable to reduce the noise as much as possible.
Japanese Patent Application Laid-Open No. 2003-070786 discloses a method of reducing speckle noise using spatial compound. In the spatial compound, an ultrasound wave is radiated at a plurality of angles. Therefore, for example, a measurement time increases and a burden on a patient increases.
As a method for reducing noise without increasing a measurement time, a reduction in noise by image processing is conceivable. “An adaptive weighted median filter for speckle suppression in medical ultrasonic images”, IEEE Vol. 36, pp. 129-135 (1989) discloses a method of removing speckle noise using a median filter. However, an image filter for removing noise sometimes blurs even a structure and a microstructure. On the other hand, a Laplacian filter and a high-boost filter are known as a filter for emphasizing a structure. Since the filters use a difference or the like, even noise is sometimes emphasized. Therefore, there is a demand for processing that can emphasize a structure while suppressing noise.
Patent Literature 1: Japanese Patent Application Laid-Open No. 2003-070786
Non Patent Literature 1: “An adaptive weighted median filter for speckle suppression in medical ultrasonic images”, IEEE Vol. 36, pp. 129-135 (1989)